Back to results
US 5,397,938 AGranted
Current mode logic switching stage
AssigneeSiemens Aktiengesellschaft
InventorsWilhelm Wilhelm, Jurgen Herrle
Life of this patent
Estimating the term…
Abstract
A current mode logic switching stage, especially an output stage for driving capacitive loads, includes a differential amplifier configuration and at least two bipolar transistors, which are connected as an emitter follower circuit to the output of the differential amplifier configuration. The emitter of one of the bipolar transistors is connected with an output of the switching stage. A controllable current source, which is controlled by a comparison device, is connected between the output and a negative supply potential. The comparison device receives emitter signals of the bipolar transistors. The current source is controlled in such a way that it impresses a high current only during a negative output signal edge. The comparison device is formed with a current mirror.
Claims12
A switching stage, comprising:
- a switching stage output;
- a differential amplifier configuration having an output;
- a first bipolar transistor being connected as an emitter follower circuit to said output of said differential amplifier configuration, said first bipolar transistor having an emitter being connected to said switching stage output;
- a controllable current source being connected between said switching stage output and a terminal for a supply potential, said controllable current source having a control input;
- a second bipolar transistor being connected as as an emitter follower circuit, being connected to said output of said differential amplifier configuration, and having an emitter;
- and
- a comparison device having a first input connected to the emitter of said first bipolar transistor, a second input connected to the emitter of said second bipolar transistor, and an output connected to said control input of said controllable current source;
- said controllable current source being controlled by said comparison device for impressing a high current with said current source if a potential of the emitter of said first bipolar transistor is higher than a potential of the emitter of said second bipolar transistor, and otherwise a low current being impressed;
- said comparison device having a current mirror circuit with an input branch and an output branch;
- said input branch and said output branch each having one first and one second terminal;
- said first terminal of said input branch being said second input of said comparison device, and said first terminal of said output branch being said first input of said comparison device;
- said input branch having a series circuit of a first resistor and a diode polarized in the conducting direction, said diode having an anode and a cathode;
- said output branch having a series circuit of a second resistor and a transistor with a base being connected to the anode of said diode, a collector being connected to said output of said comparison device, and an emitter;
- and
- the cathode of said diode and the emitter of said transistor of said output branch forming said second terminals of said comparison device and being connected to said terminal for the supply potential.
12 more elements
A switching stage, comprising:
- a switching stage output;
- a differential amplifier configuration having an output;
- a first bipolar transistor being connected as an emitter follower circuit to said output of said differential amplifier configuration, said first bipolar transistor having an emitter being connected to said switching stage output;
- a controllable current source being connected between said switching stage output and a terminal for a supply potential, said controllable current source having a control input;
- a second bipolar transistor being connected as as an emitter follower circuit, being connected to said output of said differential amplifier configuration, and having an emitter;
- and
- a comparison device having a first input connected to the emitter of said first bipolar transistor, a second input connected to the emitter of said second bipolar transistor, and an output connected to said control input of said controllable current source;
- said controllable current source being controlled by said comparison device for impressing a high current with said current source if a potential of the emitter of said first bipolar transistor is higher than a potential of the emitter of said second bipolar transistor, and otherwise a low current being impressed;
- said comparison device having a third bipolar transistor with a base, an emitter and a collector;
- resistors each being connected between said terminal for the supply potential and a respective one of the base and the emitter of said third bipolar transistor;
- the base of said third bipolar transistor being connected to said second input of said comparison device;
- and
- another resistor connected between the collector of said third bipolar transistor and said first input of said comparison device.
10 more elements
Dependencies are inferred from the claim text.